Method of manufacturing electric incandescent lamps



Sept. 21, 1948. A. w. SEITZ 1 METHOD OF MANUFACTURING ELECTRIC INCANDESCENT LAMPS Filed Oct 1, 1947 Invervtor; Aggy]? W. Seit'Z. by (flu Mk0, WW

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Patented Sept. 21', 1948 METHOD OF MANUFACTURING EL ECTRIC INCANDE SCENT LAMPS August W. Seitz, Euclid, Ohio, assignor to General Electric Company, a corporation of New York Application mm 1, 1947, Serial No. 711,337

- 5.Claims. (Cl. 316-19) My invention relates in general to electric incandescent lamps, and more particularly to a method of manufacture thereof.

In co-pending application No. 777,239. A. Greiner, filed October 1, 1947, and assigned to the assignee of the present invention, there is disclosed and claimed an electric incandescent lamp of the double-ended miniature type having terminal contact members at the opposite ends thereof and a filament supported in place in the lamp envelope by conductor wires which are fas-.

tend to the terminal contact members and are connected to the opposite ends of the filament. The procedures heretofore employed in the manufacture of such type lamps have generally involved certain operations which were unsuitable to the production manufacture of the lamps by machine methods and which accordingly rendered manufacture of such lamps costly.

It is an object therefore of the-present invention to provide an improved method .of manufacturingxan electric incandescent lamp of the above-described character which method is readily adaptable to machine production methods.

Further objects and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing in which:

Fig. l is a longitudinal section, on an enlarged scale, of an electric incandescent lamp manufactured by the method according to the invention: Fig. 2 is a detail view, in section, of the terminal cap and lead-in wire assembly for one end of the lamp; Fig. 3 is a detail view. in section. of the envelope and terminal cap assembly which is employed in the manufacture of the lamp according to the invention; Fig. 4 is aview illustrating the assembly of the envelope and terminal cap assemblies with the lead-in 'wires preparatory to -glass envelope I closed at its ends by identical metal and caps 2. 3 which are fusion-sealed to the envelope ends. The end caps-2, 3 are preferably made of silver-plated iron containing a small percentage of carbon, e. g., .05 per cent, and they are provided with peripheral lip or side wall portions 4 which fit over the ends of the glass envelope I and are fusion-sealed to the outer wall surface thereof. As shown, the glass envelope I is also sealed at its rim ends to the base wall portions 5 of the cap which base wallportions: constitute. in effect, the end walls of the envelope itself. The glass envelope I is made of a suitable low-melting point glass which matches the ex- I pansion characteristics of the metal end caps 2,3 and which readily waits and seals thereto. For scaling to silver-plated iron end caps such as are preferably employed. a softlead glass of the following approximate composition has been found to be particularly suitable:

Per cent SiOz 45 PbO A1203 2 NaaO 3 K20 14 LiaO 1 If desired, the lithium oxide in the above composition may be omitted.

The base or end walls 5 of the end caps 2,3 are formed on their outer sides withcircular bosses 8 provided with re-entrant inner wall portions or indentations I which extend inwardly of the envelope to form cone-shaped recesses! in the outer side of the cap end walls 5. At the bottoms of the recesses 8, the end cap walls 5 are provided fl extend into the envelope I. The said lead-in wires II). II are preferably made of the same silver-plated iron such as is used for the caps 2, 3, and they are electrically connected to and supported by the respective end caps by metallic fusible material or solder I2. and I3 disposed within the recesses 8 of the respective end caps 2 and 3. The lead-in wires III. II project into the envelope l longitudinally and approximately axially thereof with their inner ends spaced apart and bridged by a filament I 4 of suitable refractory metal such as tungsten. The filament Il may be either in the form of a fine linearlyextending coil or a straight length of tungsten wire. and it is preferably fastened to the lead-in wires by pressing or embedding its opposite ends into the metal of the lead-in wires. As shown.

the lead-in wires III, II are preferably formed with short laterally bent inner end portions I! to which the filament ends are fastened.

manner according to the invention, a terminal assembl l8 as shown in Fig. 2 and an envelope assembl i1 as shown in Fig. 3 are first formed separately. The terminal assembly |8 comprises end cap 2- and lead-in wire i8 united by the solder mass l2, and it may be formed by flattening one end of the lead-in wire l8 (as indicated at i8).

. inserting the wire through the aperture 8 in the end cap until the flattened and I8 rests against the rim of the'said aperture so as to be located within the cap recess 8, and then filling the recess 8 and the aperture 9 with molten solder while the part-s are held in the above-described relation with each other. Instead of soldering the wire l8 to the end cap 2, it may be secured thereto in any other suitable manner as by welding, for instance, in which case the aperture 8 in the end 'Fig. 6) -to cause the lower end of the glass tube to soften and flow down partly onto the end wall 8 of the cap 3 to thereby form the thickened glass seal portion 20. For a fuller disclosure of the manner in which the terminal and envelope assemblies l8 and I! may be formed, reference may be had to the above-mentioned co-pending Greiner application No. 777,239.

.In accordance with the invention, the completed terminal and envelope assemblies l8 and i! are next positioned and held in spaced, aligned relationship with each other, as shown in Fig. 4, with the open end of the envelope facing the inward side of the end cap 2. The two assemblies l8, I! may be held in such position in a suitable holder (not shown) which may comprise one of the heads of a turret-type machine, for instance. An extended lead-in wire 2| (which may constitute the free end portion of a supply of such wire coiled on a supply spool 22) is then inserted first through the aperture 9 in the end cap 3 and then passed through the envelope until it projects a, short distance beyond the open end of the envelope, with its end aligned with and spaced a predetermined distance from the facing inner end of the lead-in wire it) on terminal assembly It. The wires l0. 2| may be firmly held, adjacent their inner facing ends, in such aligned and spaced relation by suitable gripping jaws (not shown) provided therefor on the above-mentioned machine head. The inner end portions of the wires Ii), 2| are then ben-t laterally in the same direction to extend more or less parallel to each other and provide the laterally bent inner end portions i (Fig. 5) spaced a predetermined distance apart. The filament i3 is then suitably fastened at its ends to the bent inner ends l5 of the wires l0, 2|, as by pressing the filament wire into the metal of the said wires I0, 2|.

After the mounting of the filament i4 inplace onthe wires ll), 2|, a quantity of red phosphorus or other'getter material may be applied to the filament I, after which the terminal and envelope assemblies i8, H are brought together as shown in 'Fig. 6 and the wire 2| cut off at a point outwardly adjacent the end caps 3 to form the lead-in wire II. The assemblies i8, I? are then ready for sealing together. The lead-in wire II is kept from dropping through'the aperturel in the end caps 3 and into the envelope by the resistance of the filament H which possesses suillcient strength for such purpose. The sealing of the terminal assembly |8 to the envelope assembly I I may be performed in the same manner and with the same sealing apparatus (Fig. 6) as is used in the fabrication of the envelope assembly H, the end cap 2 being supportd in, and heated by conduction of heat thereto from, a stainless steel holder i8 which is heated by gas fires 23 from a surrounding the holder.

The unitary lamp assembly 28 (Fig. 7) thus formed is then ready for the exhaustion (also gas filling, if desired) and the final sealing-oil thereof, which operations may be conveniently carried out in a quartz exhaust chamber 28 as indicated in Fig. 7. As there shown, the lamp assembly 23 is placed and supported in an upright position,

with its unsealed end cap 3 uppermost, within the enlarged upper end 21 of a vertically extending quartz tube 28 supported within the exhaust chamber 28, with one or "more pellets 28 of a suitable silver solder disposed within the recess 8 of the end cap 3. At its lower end, the quartz exhaust chamber 26 is connected through a compression rubber chuck 30 to a vacuum lino 3| which, when opened,-evacuates the chamber 28 and also the lamp assembly 28 through the aperture 9 in the end cap 3. During the evacuation of the chamber 28, it is simultaneously heated in the region opposite the lamp assembly 28 therein, as by' gas fires 32 from burners 38, to thereby heat the lamp assembly during the exhaustion thereof, in conformance with usual lamp exhausting procedure. A fuller disclosure of the construction of the exhaust chamber 28 and the chuck 38 is given in the aforementioned co-pending Greiner application No. 777,239.

When the required degree of vacuum is produced in the lamp assembly 23. the gas fires 32 are removed and an induction coil 34 moved down over the upper end of the quartz exhaust chamber 26 so as to surround the same at a point approximately opposite the end cap .3 of the lamp assembly 25 therein. The coil 34 is then connected to a source of high frequency current. The resulting magnetic field set up by the coil 34 serves to heat the metal end cap 3 to red heat which in turn melts the solder pellet 28 by conductionof heat thereto, causing the solder to flow down into and fill the recess 8 and aperture '9 in the end cap and connect the lead-in wire II to the said cap, thus completing the manufacture of the lamp. Any excess portion of the lead-in wire projecting outwardly beyond the solder i3 (Fig. i) of the finished lamp is then cut oil flush with the outer surface thereof.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of manufacturing an electric incandescent lamp which comprises sealing an apertured metal end cap to one end of a doubleended glass envelope, fastening a lead-in conductor to another metal end cap to project from the inner side thereof, introducing an extended lead-in conductor through the apertured end cap and the associated envelope to project beyond the open end thereof, connecting the projecting ends of the lead-in conductors to the opposite ends of a filament, sealing the open end of the envelope to the said other end cap, and then exhausting the envelope through the aperture in the said apertured end cap and sealing the said aperture with metallic fusible material while the envelop is in exhausted condition.

ring burner 2| 2. The method of manufacturing an electric incandescent lamp which comprises sealing an apertured metal end cap to one end of a doubleended glass envelope to form an envelope assembly, fastening a lead-in conductor to another metal end cap to project from the inner'side thereof. and form a terminal assembly, positioning the said assemblies in spaced aligned relation with each other with the open end of the glass envelopeopposed to the inner face of the terminal assembly, introducing an extended lead-in conductor through the apertured end cap and the associated envelope to project beyond the open end thereof with the projecting end of said extended conductor spaced a predetermined dison the terminal assembly, connecting a filament across the projecting-opposed ends of the lead-in.

conductors, sealingthe open end of the glass envelope to the end cap of the terminal assembly,

, tance from the projecting end of the conductor and then exhausting the envelope through the.

aperture in the said apertured end cap and sealing the said aperture with metallic fusible material while the envelope is in exhausted condition.

3. The method of manufacturing an electric incandescent lamp which comprises sealing an apertured metal end cap to one end of a doubleended glass envelope to form an envelope assembly, fastening a lead-in conductor to another metal end cap to project from the inner side thereof and form a terminal assembly, positioning the said assemblies in spaced aligned relation with each other with the open end of the l 6 distance apart, connecting a filament across the said bent and portions of the conductors, sealing the open end of the glass envelope to the end cap of the terminal assembly, and then exhausting the envelope through the aperture in the said apertured end cap and sealing the said aperture with metallic fusible material while the envelope is in exhausted condition.

4. The method of manufacturing an electric incandescent lamp which comprises sealing an apertured metal end cap to one end of a doubleended glass envelope. fastening a lead-in conductor to another metal end cap to project from the inner side thereof, introducing an extended leadin conductor flrst through the apertured end cap and thence through the associated envelope to project beyond the open end thereof, connecting the projecting ends of the lead-in conductors to the opposite ends of a filament, sealing the open end of the envelope to the said other endcap, and then exhausting the envelope through the aperture in the said apertured end cap and sealing the said aperture with metallic fusible material while the envelope is in exhausted condition. a

apertured metal end cap to one end of a. doubleended glass envelope, fastening a lead-in conductor to another metal end cap to project from the inner side thereof, introducing the free end of a spooled lead-in conductor wire first-through the apertured end cap and thence through the associated envelope to project beyond the open end thereof, connecting the projecting ends of the lead-in-conductors to the opposite ends of a filament, sealing the open end of the envelope to the said other end cap, and then exhausting the envelope through the aperture in the said apertured end cap and sealing the said aperture with metallic fusible material while the envelope is in exhausted condition.

AUGUST W. SEITZ. 

